Socket programming : sending a file

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>



int sockfd,n,newsockfd;
char buffer[255];


void error(const char *msg)
{
	perror(msg);
	exit(1);
}

void ReceiveFile()
{
	FILE *fp=fopen("fichier.txt","ab+");
	n=read(newsockfd,buffer,255);
	printf("%s",buffer);
	fprintf(fp,"%s",buffer);
	fclose(fp);
}
void EnvoyerMessage() // SEND MESSAGE
{
	fgets(buffer,255,stdin);
	n=write(newsockfd,buffer,strlen(buffer));
	if(n<0)
	{
		error("ERROR writing to socket");
	}
	int i=strncmp("Bye",buffer,3);
}

void Chat()
{
	while(1)
	{
		bzero(buffer,256);
		n=read(newsockfd,buffer,255);
		if(n<0)
		{
			error("ERROR reading from socket");
		}

		if(strncmp(buffer,"/SEND",5)==0)
		{
			ReceiveFile();
		}
		printf("Client : %s\n",buffer);
		EnvoyerMessage();
	}
	close(newsockfd);
	close(sockfd);
}

void Serveur(char **argv)
{
	int portno;
	socklen_t clilen;
	struct sockaddr_in serv_addr,cli_addr;
	sockfd=socket(AF_INET,SOCK_STREAM,0);
	if(sockfd<0)
	{
		error("ERROR opening socket");
	}
	bzero((char *) &serv_addr,sizeof(serv_addr));
	portno=atoi(argv[1]);
	serv_addr.sin_family=AF_INET;
	serv_addr.sin_addr.s_addr=INADDR_ANY;
	serv_addr.sin_port=htons(portno);
	if(bind(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) <0)
	{
		error("ERROR on binding");
	}
	listen(sockfd,5);
	clilen=sizeof(cli_addr);
	newsockfd=accept(sockfd,(struct sockaddr *) &cli_addr,&clilen);
	if(newsockfd < 0)
	{
		error("ERROR on accept");
	}

	if(n<0)
	{
		error("ERROR reading from socket");
	}
	Chat();
}

int main(int argc,char *argv[])
{
	if(argc<2)
	{
		fprintf(stderr,"ERROR, no port provided\n");
		exit(1);
	}
	Serveur(argv);
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/stat.h>


int sockfd,n;
char buffer[256];

void error(const char *msg)
{
	perror(msg);
	exit(0);
}
void SendFile()
{
	FILE *fp;
	fp=fopen("fichier.txt","ab+");
	fgets(buffer,255,fp);
	n=write(sockfd,buffer,255);
	fclose(fp);
}
void RecevoirMessage() // RECEIVE MESSAGE
{
	bzero(buffer,256);
	n=read(sockfd,buffer,255);
	if(n<0)
	{
		error("ERROR reading from socket");
	}
	printf("Server : %s\n",buffer);
	int i=strncmp("Bye",buffer,3);
}
void Chat()
{
	while(1)
	{
		bzero(buffer,256);
		fgets(buffer,255,stdin);
		n=write(sockfd,buffer,strlen(buffer));
		if(strncmp(buffer,"/SEND",5)==0)
		{
			
			SendFile();
		}
		if(n<0)
		{
			error("ERROR writing to socket");
		}
		RecevoirMessage();
	}
}
int ConnexionServeur(char *argv[])
{
	int portno;
	struct sockaddr_in serv_addr;
	struct hostent *server;
	portno=atoi(argv[2]);
	sockfd=socket(AF_INET, SOCK_STREAM, 0);
	if(sockfd < 0)
	{
		error("ERROR opening socket");
	}
	server = gethostbyname(argv[1]);
	if(server==NULL)
	{
		fprintf(stderr,"ERROR ,no such host\n");
		exit(0);
	}
	bzero((char *) &serv_addr,sizeof(serv_addr));
	serv_addr.sin_family=AF_INET;
	bcopy((char *)server->h_addr,(char*)&serv_addr.sin_addr.s_addr,server->h_length);
	serv_addr.sin_port=htons(portno);
	if(connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
	{
		error("ERROR connecting");
	}
	Chat();
}
int main(int argc,char **argv)
{

	if(argc < 3)
	{
		fprintf(stderr,"usage %s hostname port\n", argv[0]);
		exit(0);
	}
	ConnexionServeur(argv);
}